Secondary or supporting characters should never be taken for granted. Without this intriguing group of friends, enemies, and acquaintances, we certainly wouldn't have as much fun with our protagonist.
One of the most obvious reasons why we need secondary characters is to make the storyline more interesting. Can you imagine your favorite book or movie with ONLY the protagonist throughout the entire story? It would have to be one hell of a character, and all the weight would fall on their shoulders to keep things interesting. Supporting characters also add some extra dimension and overall flavor to the story with their own unique stories and problems. The protagonists often get caught up in the middle of their dramas. In my Hernandez series, Jorge often finds himself trying to help his friends and family through their dilemmas. Of course, these characters also work with and against the main character to contribute to his story.
Not to mention that secondary characters have a way of showing you who our protagonist really is; the good and the bad. In fact, it's usually other characters that best bring out everything from rage to love in our main character, and it's always interesting to see how the protagonist reacts to these emotions. Of course, some characters contain themselves much better than others but aren't the erratic, crazy people more likely to capture our attention?
Sometimes we find ourselves falling for the secondary characters as much or more than our protagonist. That's fine too. Just because someone is the main character doesn't mean they also have to be our favorite.
